Process and apparatus for heating molten materials by injection of flames into the bath



March 1, 1966 E. PLUMAT ETAL 3,237,929

PROCESS AND APPARATUS FOR HEATING MOLTEN MATERIALS BY INJECTION 0FFLAMES INTO THE BATH Filed Dec. 5, 1961 M1 1o v ZqL/l. 181 514 UnitedStates Patent 3,237,929 PRCESS AND APPARATUS FOR HEATING ML'IENMATERIALS BY INlEtCTlUN 0F FLAMES INTO THE BATH Emile Plumat, Gilly,Pierre Eloy, Lodelinsart, and Alfred `lacobs, Montigny-sur-Sambre,Belgium, assignors to S. A. Glaverbel, Brussels, Belgium, a company ofBelgium Filed Dec. 5, 1961, Ser. No. 157,063 Claims priority,application Belgium, Dec. 9, 1960, 475,592, Patent 598,022 1t) Claims.(Cl. 2056-33) The present invention relates to a process and anapparatus for heating molten material by injecting flames or hotcombustion gases into the bath of molten products contained in thefurnace.

In a large number of furnaces for melting materials, the flames are indirect Contact with the materials to be melted. These furnaces are, forexample, those commonly called reverberatory furnaces. Regardless of theconstructional forms of these furnaces, or the type of materialscontained therein, the mode of transmission of the heat of the flamesand fumes to the bath of molten materials in such furnaces is notessentially different from one another. In such furnaces, the flames areproduced by burners on the surface of the bath contained in the furnace.Consequently, the transfer of heat takes place exclusively on thesurface of separation between the liquid and gas phases. This mode oftransmission is not satisfactory because the hottest products are on thesurface and therefore in contact with the flames, while the convectioncurrents in the bath are impeded.

Any reactions between the fumes and the molten products are inhibitedfor similar reasons. The surface layer of the bath becomes enriched inreaction products, which tends to block the desired reactions.

lt has already been proposed to inject the combustible mixture into thebath of molten products, but in doing this many difliculties areencountered. The mixture of fuel and combustion-assisting agent burnsbadly in the bath. As soon as it is introduced into the bath, themixture becomes broken up into a large number of bubbles within whichthe combustion takes place. These bubbles rise to the surface morerapidly as the bath is denser and more fluid, so that in general thetime during which the bubbles remain in the bath is short. In practice,the combustion is not complete in the bath and is completed on thesurface of the bath, which is disadvantageous, as has been shown above.Since the mixing is not effected in an exact proportion of fuel andcombustion-assisting agent in each bubble, there is an excess of onereactant or the other in each bubble.

The effect of this excess is that, on the one hand, some of thereactants do not react in the bath, and on the other hand, the speed ofreaction of the fuel and the combustion-assisting agent is reduced.

In the process according to the invention all these disadvantages areobviated.

In accordance with the invention, the combustible mixture is completelygasied and intimately mixed in a chamber, and a con-siderable proportionof the combustible mixture is burnt before being injected into the bathof molten materials.

The constituents of the mixture may be gasified by various methods. Thegasification may consist either in a vaporisation of the non-gaseousconstituent or constituents of the mixture, or in a reaction of one ormore of the constituents ysupplying gaseous reaction products, or in acombination of the aforesaid methods. The reactions giving rise to aconversion of the constitutents into gas are of at least two types. Forexample, the

3,237,929 Patented Mar. 1, 1966 fuel is dissociated into lighterfractions which are gaseous, or a combustion is effected giving gases ascombustion products.

Although a partial combustion in the mixing chamber is suicient toproduce a turbulence contributing to the mixing of the gases, theintimate mixing of the fuel, of the combustion-assisting agent and ofthe combustion products is effected by intentionally imparting whirlingmovements thereto, either by imparting to the jets of gas and/or ofliquid, directions of movement which are chosen for this purpose, orgiving the walls of the chamber curvatures which produce the sameresult.

In addition, the degree of combustion of the combustible mixture isadjusted before it is introduced into the bath of molten materials bymodifying the time for which the constituents of the mixture are incontact before being injected into the bath.

In one embodiment of the process, the supply of constituents is dividedinto two partial flows which are in contact with the other constituentfor unequal periods of time. The mean period of contact, and thereforethe degree of combustion, is then adjusted by varying the ratio of thepartial liows.

In accordance with the present invention, there are added to the mixtureof fuel and combustion-assisting agent substances which are intended tobe added to the molten materials. These substances are uniformlydispersed in the mixture like the constituents of the mixturethemselves. The oxidising or reducing character of the gases flowingthrough the bath of molten materials is adjusted by varying the ratio offuel to combustionassisting agent in the mixture. The introduction ofsubstances by this means is especially advantageous because thesubstances are thus very uniformly dispersed in the bath owing to theturbulence of the latter and the renewal of the surfaces of contactbetween the gases and the bath. Likewise, by modifying the oxidising orreducing character of the gases, a very vigorous and rapid oxidising orreducing action exerted on the bath of molten materials.

The constituents of the combustible mixture are therefore intimatelymixed and partially burnt before being introduced into the bath ofmaterials to be heated. Preferably, the degree of combusion is soadjusted that the submerged combustion is completed before the gaseousmixture leaves the bath of molten materials. The highest temperature ofthe gases is therefore developed in the bath. The surface of Contactbetween the gases and the molten materials in the bath is therefore veryextensive because the gases are occluded in numerous bubbles. Thetransfer of heat takes place rapidly owing to the high temperature ofthe gases and the considerable surface of contact. In addition, thegases leaving the bath are already at a substantially reducedtemperature, so that they heat to a less extent the walls and the roofof the furnace. In the process according to the invention, the heatlosses and the wear on the refractory materials of the furnace arereduced.

In accordance with the process, there are introduced into the mixingchamber additives intended to prevent the formation of carbon depositsor to remove these deposits, which generally form with liquid fuels,more especially with heavy fuels, such as fuel oil. These additives mayconsist of steam or of combustible materials rich in hydrogen, whichform by combustion an appreciable quantity of steam, such as methane,town gas, propane or butane. At the temperature obtaining in the mixingchamber, the steam is partially dissociated and oxidises the carbonliberated by the partial combustion of the combustible mixture. Sincethis carbon is preferably evolved in a particular region of the chamber,it is advantageous to arrange the conduit carrying the additives so thatit opens into this region.

A burner according to the invention comprises essentially aprecombustion chamber provided with conduits for the supply of fuel andcombustiomassisting agent, and also an outlet orice for the mixture offuel, combustionassisting agent and combustion products.

In some constructions, the precombustion chamber consists of a tube ofrefractory material and two cheeks or walls fitted on to the said tube.In other constructions, the chamber is a closed receptacle of refractorymaterial. The walls of the chamber are formed with orifices for Atheintroduction of fuel and combustionassisting agent into the chamber andfor discharge of the mixture. In one embodiment, the outlet orifice forthe mixture formed in the precombustion chamber is extended by a nozzleintegrally formed with the burner, the said nozzle serving to introducethe mixture into the bath of molten materials and extending through thewall of the furnace. In a preferred embodiment, the precombustionchamber is surrounded by a cooling jacket in which a uid, for examplewater, is c-irculated. The burner preferably comprises a layer ofrefractory materials between the precombustion chamber and the coolingjacket. The degree of cooling of the chamber is adjusted by choosing asthe refractory material a material of higher or lower thermalconductivity.

A precombustion chamber according to the invention is advantageouslydesigned to increase further the turbulence of the gas currentscirculating therein. This design consists in well-chosen curvaturesapplied to the walls of the chamber. Preferably, the various parts ofthe chamber have walls of different curvatures. In a preferredembodiment, the conduits carrying fuels and combustion-assisting agentlead into parts of the chamber which have different curvatures.

For example, the fuel conduit and a conduit carryingcombustion-assisting agent lead into a part of the chamber which is ofsmaller curvature, while another conduit supplying thecombustionassisting agent leads into a part of greater curvature,preferably on the axis of the conduit or of an outlet conduit for themixture formed in the chamber.

In a precombustion chamber according to the invention, the conduits forthe fuel and the combustion-assisting agent are so oriented as to inducewhirling movements. The direction of the conduits is chosen moreespecially as a function of the curvatures of the walls of the chamber.In addition, the distance between the mouths of these conduits and theoutlet conduit for the mixture is variable by displacement of theconduits within the precombustion chamber. By this means, the durationof contact of the constituents of the mixture within the chamber, andtherefore also the degree of combustion, is varied.

The degree of combustion is also varied by choosing the dimensions ofthe chamber in accordance with the type of fuel employed and moreespecially of the rate of fuel flow. In addition, the degree ofcombustion is adjusted by varying the point of introduction of the fuelinto the chamber.

In some constructions, the burners according to the invention arecombined with a supply conduit for substances intended to be introducedinto the bath of molten materials. These substances are advantageouslyintroduced into the chamber close to the point of introduction of theconstituents of the combustible mixture. Thus, the uniform-ity of theirdispersion in this mixture is generally improved. It is obvious that itis also possible to introduce them at any other point of the chamber,for example close to or in the nozzle for the ejection of the gases fromthe chamber.

The burners may also be provided with a conduit for the injection ofsteam or materials rich in hydrogen which form on combustion steam whichis intended to prevent the formation of carbon by the partial combustionof the combustible mixture. This conduit advantageously leads Cil intothat region of the mixing chamber in which the carbon tends to bedeposited.

The accompanying drawings illustrate by way of example a number ofconstructional forms of burners according to the invention.

FIGURE 1 illustrates one type of burner consisting of a tube,

FIGURE 2 illustrates a type of burner of integral form,

FIGURE 3 illustrates a burner whose chamber has been specially shapedwith a View to producing whirling currents in the mixture, and

FIGURE 4 is a section along the line IV-IV of FIG- URE 3.

In FIGURE l, the burner, which -is denoted as a whole by 1, is shown incombination with a furnace, of which a fragmentary section is shown. Theburner comprises a chamber 2 bounded by a wall 3 of refractory materialand cheeks or side walls 4 and 5 also consisting of refractory material.The wall 3 consists, for example, of a tube which is advantageously ofcircular section. A conduit 6 supplies the combustion-assisting agent,which is normally air, and if desired, preheated. A conduit 7 serves forthe injection of the fuel into the chamber 2. Preferably, the fuelemployed is a fluid, either a liquid or a gas. If a liquid fuel isemployed, it is advantageously atomised when injected into the chamber2. An atomiser 8 is then secured on the fuel supply conduit 7.Preferably, the air supply conduit 6 is concentric with the fuel supplyconduit 7. The conduits extend into `the chamber 2 by way of an orifice9 in the cheek or outer wall 4 of the burner 1. The cheek or inner wall5 positioned against the wall 10 of the furnace Iis formed with anorifice 11 through which the mixture formed in the chamber 2 isdischarged. The wall 10 is in turn formed with an orifice 12 throughwhich the mixture is injected into the bath 13 contained in the furnace.

The burner 1 is fixed to the wall of the furnace by a plate 14, forexample of metal, which is connected to the wall 10 of the furnace. Thesaid plate is formed with a hole aligned with the orifices 11 and 12,the said hole preferably being of larger diameter then the saidorifices. On the other side of the burner, a plate 16 is positionedagainst the cheek 4 and formed with an oritice 17 for the passage of theconduits 6 and 7. The plates 14 and 16 are connected by tie rods 18 andbolts 19. By tightening the said bolts, the cheeks 4 and 5 are securedagainst the tube 3 and the burner 1 is made fast with the wall 1() ofthe furnace.

In an advantageous constructional form, the combustion chamber 2 issurrounded by a cooling jacket 20, preferably consisting of sheet metal,in which there flows a cooling fluid, for ex-ample water, the conduit-sfor which are shown at 21. Banked between the wall 3 of 4theprecombustion chamber and the cooling jacket 20 is a bed or layer 22 ofa refractory material chosen from materials of higher or lower thermalconductivity, for example powdered magnesia or fibers of a veryrefractory glass. In this way, the behaviour of the refractory walls 3of the chamber is improved by reduction of their operating temperature,which is readily adjusted by variation of the thickness and the natureof the material of the bed or layer 22.

In some cases, the burner also comprises a conduit 23 for the supply ofsubstances intended to be added to the bath of molten materials. Theconduit 23 leads either into the combustion chamber 2 or into one of theconduits for the constituents of the mixture, for example the combustionair conduit, as illustrated in FIGURE 1. These substances are, forexample, oxidising agents or reducing agents employed in themetallurgical industry, or colouring agents employed in the glassindustry.

The conduit 23 also serves for introducing into the chamber 2 steam orcombustible materials rich in hydrogen which produce steam bycombustion, unless there is provided for this purpose a special conduit,which then preferably leads into that region of the chamber in which thecarbon evolved by the combustion of the combustible mixture tends to bedeposited. At the high temperature obtaining in the chamber 2, the steamreadily oxidises this carbon and thus prevents the formation of carbondeposits.

The burner operates as follows: the fuel and the combusion air areintroduced under pressure into the chamber 2 at 8 and 9 respectively. Assoon as the fuel comes into contact with the combustion air, thecombustion commences under the effect of the temperature obtaining inthe chamber 2. At least a part of the fuel is burnt, and the evolutionof heat vaporises the remainder of the fuel and may producefractionation of the fuel into additional vaporised lighter bodies. Inaddition, the various gases present in the chamber are intimately mixedby the turbulence produced by the combustion. The mixture thus createdis injected into the bath 13 of molten materials, in which it completesits combustion. The supply pressure is sufficient to compensate for thehydrostatic pressure of the bath at the level of the orifice 12. Thedegree of combustion in the chamber 2 is so adjusted that the combustionis absolutely complete at the instant when the products of combustionleave the bath 13, By adjusting the combustion in this way, the gasesare brought to their maximum temperature in the bath 13 itself, that isto say, while they are in intimate contact with the bath of moltenmaterials and while the surface of Contact between the gases and thebath is very large.

The degree of combustion in the chamber 2 is adjusted by the choice ofthe length and the volume of the chamber as a function of the rate offlow and the nature of the fuel employed. The latter adjustment of thedegree of combustion is advantageously effected by modifying thepenetration of the conduit 7 and therefore the position of the atomiser8. In this Way, the period of contact between the constituents of themixture in the combustion chamber is modified.

FIGURE 2 illustrates another type of burner suitable for the applicationof the process. It consists of a receptacle 24 consisting of refractorymaterial which bounds the chamber 2. The Said receptacle isadvantageously integrally moulded from a fused refractory material or arefractory concrete. Alternatively, it may be formed of a number ofparts joined together by means of refractory cement. The receptacle 24is extended by a nozzle 25 which injects the gases into the furnace. Thesaid nozzle is introduced into the orifice 12 in the pillar or wall ofthe furnace. The receptacle 24 is advantageously surrounded by a coolingjacket and a refractory layer 22 as stated above. In FIGURE 2, the outerface 26 is not enclosed in the jacket 20, but it is obvious that thechamber 2 may be entirely surrounded by the said jacket.

The degree of combustion is adjusted by varying the position of theatomiser 8 in the chamber 2 as described above.

FIGURES 3 and 4 illustrate a burner consisting of a member 27 ofrefractory material in which the combustion chamber 2 is formed. Thechamber is divided into two communicating zones 28 and 29, of which thezone 28 comprises walls having a smaller curvature and the zone 29comprises walls having a greater curvature. In the lower part 28, thefuel and all or part of the combustion air are tangentially introducedat 31, the air preferably surrounding the jet of fuel. Owing to thetangential introduction, the mixture is whirled in the lower part 28.The fuel partially burns.

The secondary air, if any, is introduced into the combustion chamber 2through a conduit 30 which is coaxial with the orifice 12 and leads intothe second zone 29 of hemispherical form.

The mixing of the fuel, combustion-assisting agent and combustion gasesis improved by creating currents in the 6 combustion chamber 2 by anappropriate arrangement of the conduits for the fuel andcombustion-assisting agent and by giving the chamber a profile whichpromotes the movements of the gases and of the atomised liquids. Thecurrents of gas and/or liquid are thus given a whirling movement in thechamber 2.

The secondary air blown through the conduit 30 into the zone 29 isinjected with the mixture contained in the lower zone 28 into the baththrough the orifice 12 in the pillar on wall 10 of the furnace. Thedegree of combustion in the chamber 2, and therefore the temperature ofthe chamber 2, is readily adjusted by varying the proportion of primaryair and secondary air while maintaining the chosen ratio of air to fuel.The primary air reacts, at least to an appreciable extent, with the fuelin the combustion chamber 2, while the secondary air reacts mainly withthe fuel in the bath 13, the time for which the secondary air stays inthe chamber 2 being shorter.

Of course, the invention is not limited to the embodiments which havebeen described and illustrated by way of example, and modifications maybe made thereto without departing from its scope.

We claim:

'1. The method of blowing heating gases through molten material in afurnace having a chamber for containing a bath of the molten material,comprising providing a bath of molten material in the furnace chamber,introducing separate supplies of fuel and a combustion assisting agentinto the closed combustion chamber of an adjoining auxiliary furnace soas to produce Within such combustion chamber from such constituents anintimate mixture of partially burnt, completely gaseous, combustiblematerial, and injecting such partially burnt gaseous mixture into thebath of molten material in the furnace chamber at a place located belowthe upper surface of said bath to enable complete combustion of suchmixture within the bath as it rises towards the upper surface of thelatter and before the gases escape through the upper surface of suchbath, whereby the combustion within the bath imparts heat to said bath.

2. The method of blowing heating gases through molten material in afurnace having a chamber for containing a `bath of the molten material,comprising providing a bath of molten material in the furnace chamber,introducing separate supplies of fuel and a combustion assisting agentinto the closed combustion chamber of an adjoining auxiliary furnace soas to produce within such combustion chamber from such constituents anintimate mixture of partially burnt, completely gaseous, combustiblematerial, and injecting such partially burnt gaseous mixture into thebath of molten material in the furnace chamber at a place located belowthe upper surface of said bath to enable the combustion of such mixtureto continue within the ybath during its rise towards the upper surfaceof the latter, whereby the combustion within the bath imparts heat tosaid bath.

3. The method defined in claim 2 in which at least one of saidconstituents upon its entry into the closed combustion chamber is causedto travel therein with such whirling movements as will cause the saidconstituents to become intimately intermixed.

4. The method defined in claim 2 in which the period of contact betweenthe constituents in the combustion chamber is controlled to give theresulting gaseous combustible material produced therefrom a givenpreburnt condition before injection thereof into the bath of moltenmaterial.

S. The method defined in claim 4, in which the period of contact betweenthe constituents is effected by dividing the flow of one of theconstituents into a number of partial flows and bringing such partialflows of such one constituent into contact with the other constituentfor different lengths of time.

6. The method defined in claim 2 including introducing into the closedcombustion cham-ber with the constituents d an ingredient capable ofinhibiting the formation of substantial carbon deposits upon the wallsof such chamber.

7. Apparatus for heating molten materials, comprising a furnace having achamber for containing a bath of molten material, an auxiliary furnaceadjacent to one wall of said furnace chamber and having a closedcombustion chamber, means for introducing into said combustion chamberseparate supplies of fuel and a combustion assisting agent so as toproduce within such chamber lfrom such constituents an intimate mixtureof partially burnt, completely gaseous, combusti-ble material, means forin jecting the partially burnt gaseous mixture of combustible materialproduced in said combustion chamber into the bath of molten material insaid furnace chamber at a place located below the upper surface of saidbath to enable the combustion of such mixture to continue within thebath during its rise towards the upper surface of the latter to impartheat to the bath, theV means for supplying one of the constituents intosaid combustion chamber being selectively movable relative to the meansfor supplying the other of the constituents therein to control thepreburnt condition of the gaseous combustible material discharged fromsuch chamber into the bath of molten material.

8. Apparatus such as defined in claim 7, in which the means forsupplying the constituents are constructed and arranged to introducesuch constituents into the combustion chamber so that one of suchconstituents is discharged into the path of flow of the otherconstituent at a place spaced from the place of entry of such otherconstituent.

9. Apparatus such as defined in claim 7, in which the walls of saidcombustion chamber are configured to impart O 0 to at least one of suchconstituents a whirling movement such as will cause an intimate mixtureof such constituents. 10. Apparatus such as defined in claim 7 in whichsaid means for injecting the partially burnt gaseous mixture ofcombustible material into the bath of molten material extends throughsaid one side wall of said furnace at a place in which the supplypressure of such combustible material is sufficient to compensate forthe hydrostatic pressure of the bath at the level of the dischargeorifice of such injecting means, and in which said constituentintroducing means includes at least one constituent supply means capableof discharging such one constituent into said combustion chamber so thatthe entry liow thereof is substantially aligned with the axis of thedischarge orice of such injecting means.

References Cited by the Examiner UNITED STATES PATENTS 1,656,723 1/1928Call 266-41 2,333,654 11/1943 Lellep 266-35 2,526,472 10/1950 Gilliland266-34 2,833,643 5/1958 Newman 266-29 2,878,644 3/1959 Fenn 126-360 X2,906,616 9/1959 Alland et al. 75-52 3,034,887 5/1962 Henne 266-353,060,015 10/1962 Spolders et al 75-60 WHITMORE A. WILTZ, PrimaryExaminer.

RAY K. WINDHAM, Examiner.

F. R. LAWSON, J. C. HOLMAN, P. M. COHEN,

Assistant Examiners.

1. THE METHOD OF BLOWING HEATING GASES THROUGH MOLTEN MATERIAL IN A FURNACE HAVING A CHAMBER FOR CONTAINING A BATH OF THE MOLTEN MATERIAL, COMPRISING PROVIDING A BATH OF MOLTEN MATERIAL IN THE FURNACE CHAMBER, INTRODUCING SEPARATE SUPPLIES OF FUEL AND A COMBUSTION ASSISTING AGENT INTO THE CLOSED COMBUSTION CHAMBER OF AN ADJOINING AUXILIARY FURNACE SO AS TO PRODUCE WITHIN SUCH COMBUSTION CHAMBER FROM SUCH CONSTITUENTS AND INTIMATE MIXTURE OF PARTIALLY BURNT, COMPLETELY GASEOUS, COMBUSTIBLE MATERIAL, 